第2步：捉迷藏，kafka的main入口在哪里？

第2步：捉迷藏，kafka的main入口在哪里？

1、看一下启动kafka的脚本
nohup /usr/local/kafka_2.10-0.9.0.1/bin/kafka-server-start.sh  /usr/local/kafka_2.10-0.9.0.1/config/server.properties &

我们看一下bin目录下的kafka-server-start.sh脚本：
if [ $# -lt 1 ]; //参数的个数小于1
then
 echo "USAGE: $0 [-daemon] server.properties [--override property=value]*"
 exit 1
fi
base_dir=$(dirname $0)

if [ "x$KAFKA_LOG4J_OPTS" = "x" ]; then
    export KAFKA_LOG4J_OPTS="-Dlog4j.configuration=file:$base_dir/../config/log4j.properties"
fi

if [ "x$KAFKA_HEAP_OPTS" = "x" ]; then
    export KAFKA_HEAP_OPTS="-Xmx1G -Xms1G"
fi

EXTRA_ARGS="-name kafkaServer -loggc"

COMMAND=$1
case $COMMAND in
  -daemon)
    EXTRA_ARGS="-daemon "$EXTRA_ARGS
    shift
    ;;
  *)
    ;;
esac

exec $base_dir/kafka-run-class.sh $EXTRA_ARGS kafka.Kafka "$@"

//要看一下kafka-run-class.sh  kafka.Kafka类

2、看一下kafka创建topic的脚本kafka-topics.sh

kafka-topics.sh --create --zookeeper master:2181,worker1:2181,worker2:2181 --replication-factor 1 --partitions 1 --
topic SparkStreamingDirected
 
kafka-topics.sh 只有一句话

exec $(dirname $0)/kafka-run-class.sh kafka.admin.TopicCommand "$@"
linux说明：
$0：Shell本身的文件名
$@：表示所有脚本参数的内容
$#:表示返回所有脚本参数的个数。

要看kafka-run-class.sh脚本 kafka.admin.TopicCommand

4、kafka-run-class.sh 探秘

 

if [ $# -lt 1 ];
then
  echo "USAGE: $0 [-daemon] [-name servicename] [-loggc] classname [opts]"
  exit 1
fi

base_dir=$(dirname $0)/..

if [ -z "$SCALA_VERSION" ]; then
 SCALA_VERSION=2.10.5
fi

if [ -z "$SCALA_BINARY_VERSION" ]; then
 SCALA_BINARY_VERSION=2.10
fi

# run ./gradlew copyDependantLibs to get all dependant jars in a local dir
shopt -s nullglob
for dir in $base_dir/core/build/dependant-libs-${SCALA_VERSION}*;
do
  CLASSPATH=$CLASSPATH:$dir/*
done

for file in $base_dir/examples/build/libs//kafka-examples*.jar;
do
  CLASSPATH=$CLASSPATH:$file
done

for file in $base_dir/clients/build/libs/kafka-clients*.jar;
do
  CLASSPATH=$CLASSPATH:$file
done

for file in $base_dir/tools/build/libs/kafka-tools*.jar;
do
  CLASSPATH=$CLASSPATH:$file
done

for dir in $base_dir/tools/build/dependant-libs-${SCALA_VERSION}*;
do
  CLASSPATH=$CLASSPATH:$dir/*
done

for cc_pkg in "api" "runtime" "file" "json"
do
  for file in $base_dir/connect/${cc_pkg}/build/libs/connect-${cc_pkg}*.jar;
  do
    CLASSPATH=$CLASSPATH:$file
  done
  if [ -d "$base_dir/connect/${cc_pkg}/build/dependant-libs" ] ; then
    CLASSPATH=$CLASSPATH:$base_dir/connect/${cc_pkg}/build/dependant-libs/*
  fi
done

# classpath addition for release
CLASSPATH=$CLASSPATH:$base_dir/libs/*

for file in $base_dir/core/build/libs/kafka_${SCALA_BINARY_VERSION}*.jar;
do
  CLASSPATH=$CLASSPATH:$file
done
shopt -u nullglob

# JMX settings
if [ -z "$KAFKA_JMX_OPTS" ]; then
  KAFKA_JMX_OPTS="-Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.authenticate=false  -Dcom.sun.management.jmxremote.ssl=false "
fi

# JMX port to use
if [  $JMX_PORT ]; then
  KAFKA_JMX_OPTS="$KAFKA_JMX_OPTS -Dcom.sun.management.jmxremote.port=$JMX_PORT "
fi

# Log directory to use
if [ "x$LOG_DIR" = "x" ]; then
    LOG_DIR="$base_dir/logs"
fi

# Log4j settings
if [ -z "$KAFKA_LOG4J_OPTS" ]; then
  # Log to console. This is a tool.
  KAFKA_LOG4J_OPTS="-Dlog4j.configuration=file:$base_dir/config/tools-log4j.properties"
else
  # create logs directory
  if [ ! -d "$LOG_DIR" ]; then
    mkdir -p "$LOG_DIR"
  fi
fi

KAFKA_LOG4J_OPTS="-Dkafka.logs.dir=$LOG_DIR $KAFKA_LOG4J_OPTS"

# Generic jvm settings you want to add
if [ -z "$KAFKA_OPTS" ]; then
  KAFKA_OPTS=""
fi

# Which java to use
if [ -z "$JAVA_HOME" ]; then
  JAVA="java"
else
  JAVA="$JAVA_HOME/bin/java"
fi

# Memory options
if [ -z "$KAFKA_HEAP_OPTS" ]; then
  KAFKA_HEAP_OPTS="-Xmx256M"
fi

# JVM performance options
if [ -z "$KAFKA_JVM_PERFORMANCE_OPTS" ]; then
  KAFKA_JVM_PERFORMANCE_OPTS="-server -XX:+UseG1GC -XX:MaxGCPauseMillis=20 -XX:InitiatingHeapOccupancyPercent=35 -XX:+DisableExplicitGC -Djava.awt.headless=true"
fi

while [ $# -gt 0 ]; do
  COMMAND=$1
  case $COMMAND in
    -name)
      DAEMON_NAME=$2
      CONSOLE_OUTPUT_FILE=$LOG_DIR/$DAEMON_NAME.out
      shift 2
      ;;
    -loggc)
      if [ -z "$KAFKA_GC_LOG_OPTS" ]; then
        GC_LOG_ENABLED="true"
      fi
      shift
      ;;
    -daemon)
      DAEMON_MODE="true"
      shift
      ;;
    *)
      break
      ;;
  esac
done

# GC options
GC_FILE_SUFFIX='-gc.log'
GC_LOG_FILE_NAME=''
if [ "x$GC_LOG_ENABLED" = "xtrue" ]; then
  GC_LOG_FILE_NAME=$DAEMON_NAME$GC_FILE_SUFFIX
  KAFKA_GC_LOG_OPTS="-Xloggc:$LOG_DIR/$GC_LOG_FILE_NAME -verbose:gc -XX:+PrintGCDetails -XX:+PrintGCDateStamps -XX:+PrintGCTimeStamps "
fi

# Launch mode
if [ "x$DAEMON_MODE" = "xtrue" ]; then
  nohup $JAVA $KAFKA_HEAP_OPTS $KAFKA_JVM_PERFORMANCE_OPTS $KAFKA_GC_LOG_OPTS $KAFKA_JMX_OPTS $KAFKA_LOG4J_OPTS -cp $CLASSPATH $KAFKA_OPTS "$@" > "$CONSOLE_OUTPUT_FILE" 2>&1 < /dev/null &
else
  exec $JAVA $KAFKA_HEAP_OPTS $KAFKA_JVM_PERFORMANCE_OPTS $KAFKA_GC_LOG_OPTS $KAFKA_JMX_OPTS $KAFKA_LOG4J_OPTS -cp $CLASSPATH $KAFKA_OPTS "$@"
fi

前面一大堆参数略过了，最后的一行启动模式 Launch mode。

exec $JAVA $KAFKA_HEAP_OPTS $KAFKA_JVM_PERFORMANCE_OPTS $KAFKA_GC_LOG_OPTS $KAFKA_JMX_OPTS $KAFKA_LOG4J_OPTS -cp $CLASSPATH $KAFKA_OPTS "$@"

5、启动后就到了kafka的类入口了。

启动kafka的main入口：kafka.kafka

kafka建立topic的入口：kafka.admin.TopicCommand